title: Motor Unit Number Index (MUNIX): a novel neurophysiological marker for neuromuscular disorders; test-retest reliability in healthy volunteers.
abstract: OBJECTIVE
  To investigate the intra-rater and inter-rater test-retest reliability of the Motor Unit Number Index (MUNIX) in healthy subjects in a multicentre setting.
  
  
  METHODS
  Six study centres applied the MUNIX technique in 66 healthy subjects. Five to six muscles (biceps brachii, BB; abductor digiti minimi, ADM; abductor pollicis brevis, APB; tibialis anterior, TA; extensor digitorum brevis, EDB and abductor hallucis, AH) were measured in each volunteer four times by two independent examiners.
  
  
  RESULTS
  The method was easy to perform and well tolerated. The intraclass correlation coefficient (ICC) varied between centres and muscles. Intra-rater reliability was greatest for the AH (ICC 0.83) and EDB (ICC 0.81). Inter-rater reliability was greatest for the AH (ICC 0.69) and ADM muscles (ICC 0.69). The most critical muscle was the APB muscle (ICC 0.52, total variability). This was mostly due to variability in the compound muscle action potential (CMAP) measurements. MUNIX values of the APB, ADM and TA fell into the same range as in other motor unit number estimation (MUNE) studies.
  
  
  CONCLUSIONS
  MUNIX measurements in multiple muscles show good inter- and intra-rater reliability in healthy subjects. CMAP amplitude must be controlled to optimize reliability.
  
  
  CONCLUSIONS
  Results suggest that MUNIX could serve as a reliable marker for motor neuron loss in diseases like amyotrophic lateral sclerosis.
authors.affiliation: Neuromuscular Diseases Unit, Kantonsspital St Gallen, St Gallen, Switzerland. christoph.neuwirth@kssg.ch
authors.forename: Christoph
authors.initials: C
authors.lastname: Neuwirth
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Nandedkar
authors.forename: Erik
authors.initials: E
authors.lastname: Stålberg
authors.forename: Paul E
authors.initials: PE
authors.lastname: Barkhaus
authors.forename: Mamede de
authors.initials: Md
authors.lastname: Carvalho
authors.forename: Jasna
authors.initials: J
authors.lastname: Furtula
authors.forename: Johannes P van
authors.initials: JP
authors.lastname: Dijk
authors.forename: Reto
authors.initials: R
authors.lastname: Baldinger
authors.forename: José
authors.initials: J
authors.lastname: Castro
authors.forename: João
authors.initials: J
authors.lastname: Costa
authors.forename: Marit
authors.initials: M
authors.lastname: Otto
authors.forename: Arne
authors.initials: A
authors.lastname: Sandberg
authors.forename: Markus
authors.initials: M
authors.lastname: Weber
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation*; D009468:Neuromuscular Diseases / Q000175:diagnosis*; D015203:Reproducibility of Results; D055815:Young Adult